1. Field of the Invention
The present invention relates to a projection exposure apparatus and method, which can be applied, for example, to applications of projecting a large-area pattern onto a photosensitive substrate used for fabricating a liquid crystal display board.
2. Related Background Art
Conventional projection type exposure apparatus were arranged to calibrate the imaging characteristic of its projection optical system by printing an image of a mask or the like, in which measurement patterns were written at a plurality of positions preliminarily determined, on a photosensitive substrate. Then the imaging characteristic of the projection optical system was modified (or adjusted) based on an amount of positional deviation from an ideal position, obtained by the measurement of the position of the measurement pattern images formed on the substrate.
If the apparatus employed a method for measuring the position of pattern through the projection optical system (which is the so-called TTL method) as shown in FIG. 13, a light beam emitted from an illumination light source 1 for exposure was routed through a fiber 2 or the like to a substrate table 3 so as illuminate a fiducial mark plate FM and to conduct the light passing through the plate FM to enter the projection optical system 4. Having passed through the projection optical system 4, the light beam then passed through the measurement pattern portion of mask 5 and entered a photosensor 6. An amount of positional deviation was detected based on the light intensity detected by the photosensor 6 and the position of substrate table 3, and the imaging characteristic of the projection optical system was modified based on the amount of positional deviation.
However, the method of calibrating the imaging characteristic of the projection system 4 by exposure, development, and measurement of the substrate using the test mask or the like, in which the measurement patterns were written, as described above, had problems that the exposure, development, and measurement required a lot of labor and time and were complicated and that measuring equipment for the substrate needed to be taken account of.
On the other hand, the method of calibrating the imaging characteristic by the TTL method had such a drawback that configurations for illumination of and around the substrate table 3 were complicated because of the routing of the illumination light beam for exposure through the fiber 2 etc.